That’s what Paton and Larkin mean: the effect of Harris and Klebold’s example was to make it possible for people with far higher thresholds—boys who would ordinarily never think of firing a weapon at their classmates—to join in the riot.

“But group interaction was such that none could admit this without loss of status; in our terms, their threshold for stealing cars is low because daring masculine acts bring status, and reluctance to join, once others have, carries the high cost of being labeled a sissy.” You can’t just look at an individual’s norms and motives. You need to look at the group.

This might also be the same case with fraternity shenanigans and even more deplorable actions like gang rapes. Usually there's one or more sociopaths that start the movement, and then others reluctantly join in.

Most previous explanations had focussed on explaining how someone’s beliefs might be altered in the moment.

Knowing a little of what is coming in advance here, I can't help but thinking: How can this riot theory potentially be used to influence politics and/or political campaigns? It could be particularly effective to get people "riled up" just before a particular election to create a political riot of sorts and thereby influence the outcome.

Facebook has done several social experiments with elections in showing that their friends and family voted and thereby affecting other potential voters. When done in a way that targets people of particular political beliefs to increase turn out, one is given a means of drastically influencing elections. In some sense, this is an example of this "Riot Theory".